Bring a large pot of lightly salted water to boil. Add linguini and cook until just tender, about 8-10 minutes. While this occurs, heat the oil in a large skillet over medium heat. Add the bell peppers and onion and cook until just tender, about 3-4 minutes. Add the snap peas and cook 1 minute more, then stir in sauce and bring to a gentle simmer. When pasta is cooked drain well, then add to the sauce, gently tossing. Spoon the linguini on a serving platter, top with grilled or roasted sausages, and serve. Serve freshly grated Parmesan Reggiano cheese at the table to sprinkle on top.